On the basis of pilot study results indicating that post-menopausal women with vertebral crush fractures have significantly decreased androgen production rates, we will measure androgen and estrogen production rates in post-menopausal women with vertebral crush fractures and compare these with an age and weight-matched control population. In order to see whether there are correlations between androgens and estrogens and the rate of bone loss, we will measure androgen and estrogen production rates 2-3 times in a group of post-menopausal women and correlate these rates with the rate of bone loss calculated from changes in radial bone mass during a five-year period of study. We also propose to examine femurs of mice for estrogen receptors to extend our preliminary findings.